Simple TK Question - refreshing the canvas when not in focus

[Eric Brunel]

On Tue, 29 Apr 2008 15:22:12 +0200, blaine <frikker at gmail.com> wrote:

> Hey everyone!
>   I'm not very good with Tk, and I am using a very simple canvas to
> draw some pictures (this relates to that nokia screen emulator I had a
> post about a few days ago).
>
> Anyway, all is well, except one thing.  When I am not in the program,
> and the program receives a draw command (from a FIFO pipe), the canvas
> does not refresh until I click into the program. How do I force it to
> refresh, or force the window to gain focus?  It seems like pretty
> common behavior, but a few things that I've tried have not worked.
>
> Class screen():
>     def __init__(self):
>         self.root = Tkinter.Tk()
>         self.root.title('Nokia Canvas')
>         self.canvas = Tkinter.Canvas(self.root, width =130,
> height=130)
>         self.canvas.pack()
>         self.root.mainloop()
>
> Then somewhere a long the line I do:
>             self.canvas.create_line(args[0], args[1], args[2],
> args[3], fill=color)
>             self.canvas.pack()

Unrelated question: why are you doing a .pack() again here? Packing the  
widget just inserts it at the right place in its container, so you only  
have to do it once. So the one you did in __init__ is enough.

> I've tried self.root.set_focus(), self.root.force_focus(),
> self.canvas.update(), etc. but I can't get it.

IIRC:
- self.root.set_focus() will only work if your application already has the  
focus, so it's not what you need here.
- self.root.force_focus() is usually considered as evil: it'll give the  
focus to your application whatever the user is doing, which is usually  
*really* annoying. So I guess a lot of window managers just refuse to do  
it; this may be what happens here.

But self.canvas.update() should work. If it doesn't, then there are  
probably limitations on your platform that prevents it to work... Do you  
happen to have other applications that can update their display while they  
don't have the focus? Do they have the same problem? If they do, it's  
probably a limitation on the platform and I guess you won't be able to do  
anything about it... BTW, what platform are you on?

> Thanks!
> Blaine

HTH
-- 
python -c "print ''.join([chr(154 - ord(c)) for c in  
'U(17zX(%,5.zmz5(17l8(%,5.Z*(93-965$l7+-'])"